The invention relates to a double passenger seat support arrangement for seat installations in buses, boats and airplanes which include a support base having at least two seats supported thereon with backrests mounted on the seats and at least one of the seats being transversely movable on the support base.
Like normal furniture seats, passenger seats for the transportation of people need to be comfortable and attractive in appearance but they also must be safe for their intended use. Vehicle passenger seats are subjected to substantially rougher wear and tear than furniture seats; they need to be very sturdy and yet they need to absorb impact energy resiliently and without breakage. They also should remain rattle-free over a long period of use and nevertheless they need to be light in weight. Another requirement is that the seats should be economic to manufacture and to operate by offering the possibility of exchanging any parts subject to wear. Furthermore, such passenger seats should be easy to mount and be adaptable to various space arrangements, and they should finally require only small volumes such that they can be easily shipped in knocked down state in large quantities.
None of the presently available passenger seats meets all these requirements. Generally passenger seats presently built are so rugged that they meet the strength requirements over their full projected life, that is, they remain rattle-free over a long time of use. This results in the construction of not only relatively heavy but also very expensive seats providing also for a relatively high dead weight of the vehicles equipped with such seats. Furthermore, such seats are generally manufactured in accordance with special requirements depending on a particular application.
In addition to the requirements mentioned above, passenger seats should be designed such that they can be arranged behind one another as closely as possible for economical reasons. Nevertheless there should be sufficient leg room for good seating comfort--in spite of a close spacing of the seats--for which the height of the space under the seats is responsible to a large degree. Since however, the height of the seating surface is essentially determined by the human anatomy and since the seats have to have a given minimum upholstery thickness, it is only possible to improve the leg room or rather the height of the space under a seat by making the laterally extending seat support structure as flat as possible.
It has been tried earlier to provide between two support legs a single lateral support beam which however must be very sturdy in order to meet all the requirements. However experience has shown that such a single beam, no matter how sturdy, cannot withstand the high torsional load to which it is exposed during an accident. Modern vehicle seat support arrangements include therefore always two spaced support structures or an especially formed plate structure extending between the support legs for supporting the seat members.
In determining the height of the seat support base also the height of the adjustment tracks which permits lateral position adjustment of at least one of the seats and which is arranged on top of the seat support base and below the seat members needs to be taken into consideration. A very good solution which generally meets all requirements is shown in U.S. Pat. No. 4,422,691. The arrangement presented therein utilizes two spaced parallel profiled beams which have a double C cross-section and extend across the base legs. This arrangement provides for two guide grooves for mounting bolts permitting connection thereof to the base legs and also to the seat members at any desired distance.
The two beams may even be reinforced by a plate structure extending between and interconnecting the beams. A disadvantage of this arrangement however is that the structure is relatively high which nevertheless cannot be avoided for reasons of stability and rigidity.
The arrangement as shown in U.S. Pat. No. 4,761,036 is considered to be an improvement in this respect in that sturdiness of a double C-shaped beam structure is obtained by embedding the C-shaped rods in a profile rod which includes two continuous closed box spars.
Since the rigidity of this beam structure is obtained mainly by the box spars the beam structure may be relatively low for a given load. But like in the previously described arrangement the adjustment tracks are disposed on top of the beam structure or the support plate so that the height of the complete arrangement including the height of the adjustment tracks is quite large since the height of the adjustment tracks has to be added to the height of the support beam structure, that is, the leg room is accordingly smaller.
It is the principal object of the present invention to provide an arrangement in which the support rod or plate structures are so formed that the total height of the support structure--with or without adjustment track--is very small such that the arrangement provides for improved leg room without losing the required rigidity.